Controlled impedance connector



Dec. 2, 1969 M. SCHNECK 3 CONTROLLED IMPEDANCE CONNECTOR Filed Aug. 29, 1967 2 Sheets-Sheet l INVENTOR. MART/IV .SCHNE'C'K Dec. 2, 1969 M. SCHNECK 3,482,201

' CONTROLLED IMPEDANCE CONNECTOR Filed Aug. 29, 1967 2 Sheets-Sheet 2 34 no.7 20 i8 42 Z4 1 N VEN TOR. MART/N sch NECK AITTQRA EFS United States Patent 3,482,201 CONTROLLED IMPEDANCE CONNECTOR Martin Schneck, Old Bridge, N..I., assignor to Thomas & Betts Corporation, a corporation of New Jersey Filed Aug. 29, 1967, Ser. No. 664,192 Int. Cl. H011 3/06, 13/50 US. Cl. 339-14 8 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION In many electrical and electronic applications, it is desirable to maintain a constant, predetermined, controllable impedance along the length of a line or in electrical connections between lines. This is especially true in small signal applications where variations in impedance result in signal distortion and electrical losses. Typical small signal applications utilize twisted wire pairs to carry the signals, one of the wires being at ground potential and the other wire being at some other potential. Where a plurality of twisted wire pairs are used, it is common to ground all of the ground wires to a common ground bus bar or the like.

Multiconductor flat cable has been widely used as a substitute for a plurality of individual twisted wire pairs, since it is compact, versatile and provides more reliable control of the critical parameters. In multiconductor fiat cable, a plurality of spaced adjacent conductors are disposed in substantially a flat insulating medium. An individual twisted wire pair is represented by two adjacent conductors in the cable, one of which is normally grounded and the other of which is at a dilferent potential.

In terminating the cable, it is desirable that electrical losses be minimized and that the impedance of the cable be controlled in the terminated connection. It is also desirable that each conductor of a pair which is at ground potential be terminated to a common ground.

SUMMARY OF INVENTION It is thus an object of the present invention to provide a new and improved connector which provides a controlled impedance.

It is a further object of the present invention to provide a connector for multiconductor flat cable which may be easily assembled and economically manufactured.

It is another object of the present invention to provide a controlled impedance connector for multiconductor fiat cable which provides positive connection with the conductors of multiconductor cable terminated by said connector.

It is yet another object of the present invention to provide a controlled impedance connector for multiconductor flat cable which is adapted to terminate and connect two multiconductor cables to each other.

It is still another object of the present invention to provide a controlled impedance connector for multiconductor flat cable which may be adapted to different characteristic impedances of cables by proper choice of the dimensions and materials of the connector.

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Other objects and a fuller understanding of the invention will be evident to those skilled in the art from the description and drawings.

In general, the controlled impedance connector of the present invention comprises an outer housing comprising two half-shells and an inner connector assembly positioned within said housing. The inner connector assembly comprises a ground plane spring and a plurality of individual spring elements spaced from the ground plane spring by a dielectric block. A- pair of slotted outer blocks sandwich the spring-dielectric block combination and are adapted to fit into the half-shells of the outer housing. By controlling the dimensions and material of the dielectric spacer block and the depth and width of the spring elements, a particular impedance for the connector may be determined. Means are provided for locking the inner connector assembly into the half-shells of the housing and means are also provided for securing the two half-shells of the housing together.

DESCRIPTION OF DRAWINGS In the drawings:

FIG. 1 is a perspective view of a preferred embodiment of the connector of the present invention;

FIG. 2 is an exploded view of the connector of FIG. 1 showing the inner assembly of the connector;

FIG. 3 is a partially sectional exploded view showing the elements of the inner assembly of the connector of FIG. 1;

FIG. 4 is an exploded view showing the ground plane sprain and spring elements of the connector of the present invention;

FIG. 5 is a partially sectional elevational view taken along line 55 of FIG. 1;

FIG. 5a is a partially sectional perspective view of a spring element shown in FIG. 5;

FIG. 6 is a partially sectional top plan view of the connector of FIG. 1; and

FIG. 7 is a partially sectional partially broken-away elevational rear view of the connector of FIG. 1.

GENERAL DESCRIPTION OF THE EMBODIMENT Referring more particularly now to the drawings, there is shown a preferred embodiment of the controlled impedance connector of the present invention. As shown, an outer housing comprising two half-shells of insulating material 10 and 12 house an inner connector assembly 14 adapted to be positioned within shells 10 and 12. Each of shells 10 and 12 are substantially identical and are provided with an axially running slot on the outer face thereof. An inner chamber 16 opens out onto slot 18 of shell 10 (see FIG. 5). In like manner, chamber 20 of shell 12 opens out onto slot 22 of shell 12.

Shells 10 and 12 are provided with wings 24 which have channels or holes 26 which are adapted to have suitable fasteners (not shown) passed therethrough to secure shells 10 and 12 together after inner assembly 14 has been positioned within shells 10 and 12. Any suitable fastener such as screws, rivets, eyelets, bolts or the like may be used.

Inner connector assembly 14 comprises a first insulator block 28 of generally rectangular elongated shape. A ground plane spring comprising a generally elongated rectangular central portion 32 and a plurality of spring elements 34 projecting transversely of central portion 32 provides a grounding connection for the ground conductors of a multiconductor flat cable terminated to the connector. A dielectric spacer bar having a generally rectangular elongated central portion 36 and transverse end portions 38 and 40 sandwichesground plane spring 30 between itself and lower bar 28. Next is provided a plurality of individual spring elements 42 which, prior to assembly, are connected at their ends by elongated strips 44. Elongated strips 44 are severed from springs 42 after assembly of assembly 14. Completing inner assembly 14 is an elongated bar which is provided with a plurality of slots 43 adapted to hold spring elements 42 in position. As will be described hereinafter, the thickness and material of spacer block 36, as well as the thickness and width of spring elements 42, determine the characteristic impedance of the connector.

As shown in FIG. 2, after assembly of the elements of connector assembly 14, the assembly is ready to be inserted Within shells 10 and 12. The spring elements 42 and ground plane spring 32 are locked within shells 10' and 12 by means of locking elements 50 provided within chambers 16 and 20 respectively of shells 10 and 12. These locking elements are adapted to bear against the shoulders provided by recessess 52 in the ends of spacer bar 36. This locking action is shown more clearly in FIG. 6, wherein the projecting portion 54 of locking elements 50 is shown abutted against shoulder 56 of recess 52. This locking action between half-shells 10 and 12 and inner assembly 14 minimizes accidental disassembly of the connector before shells 10 and 12 are secured together externally by suitable fasteners.

The inner surfaces of shells 10 and 12 are also provided with a plurality of notches 58 adapted to receive the spring elements 42 and elements 34 or ground plane spring 30. This is to insure proper positioning of the spring elements within half-shells 10 and 12.

The characteristic impedance of the connector is determined by the distance between the ground plane spring and spring elements, by the thickness and width of the spring elements, and by the dielectric material used in the spacer block. This is more clearly shown in FIG- URES and 5A, where D represents the distance between ground Spring 30 and spring element 42 (FIG. 5); t represents the thickness of spring element 42 and w represents the width of spring element 42 (5A). Characteristic impedance may then be determined by means of the following formula:

where Z, represents the characteristic impedance of the connector, w represents the width of spring element 42, D represents the distance between the bottom of spring element 42 and ground plane spring 30, and t represents the thickness of spring element 42. Thus, by use of this formula, any desired characteristic impedance may be produced by proper selection of the spring elements and spacing between the ground plane spring and the spring elements.

As shown in FIG. 5, spring elements 42 and elements 34 of spring 30 are curved inwardly toward each other to provide positive contact with the conductors of multiconductor flat cable or printed circuit board brought into contact with these elements. Thus the spacing between the nearest portions of spring elements 42 and 34 is such that positive contact may be made. As shown, the conductors of a multiconductor cable 60 are stripped at the ends and bent over a rigid board 62. Only the upper surfaces are stripped of insulation so that an insulating backing on the lower surface of the plurality of conductors of cable 60 provides for lateral support of the conductors 64. The outer thickness of cable 60 bent around board 62 is seen to be less than the distance be tween the closest portions of elements 42 and 34, so that when board 62 with cable 60 thereon is inserted into the connector of the present invention, positive contact will be made between the spring elements and the con ductors of the cable. The spring elements 34 of ground plane spring 30 are staggered with respect to spring elements 42 so that when conductor cable is inserted into half-shell 10, the spring elements of ground plane spring 30 will contact the ground conductors of the pair of conductors of cable 60. In this manner, all of the ground conductors of cable 60 will be commonly grounded through ground plane spring 30. On the other hand, since there is no common connection between spring elements 42, there will be a direct connection between individual conductors of the cable to complementary conductors on a second cable or printed circuit board inserted into shell 12.

The staggering of elements 34 and elements 42 is shown more clearly in FIG. 7. There is also shown the staggering of the slots of the upper and lower inner surfaces respectively of inner chamber 20 of half-shell 12 and inner chamber 22 of half-shell 10 to accommodate respectively the spring elements 34 and 42.

As shown in FIG. 5, slots 18 and 22 respectively of shells 10 and 12 are chamfered at the entrance thereof to facilitate insertion and removal of conductor cable.

What is claimed is:

1. An electrical connector comprising a housing, said housing having a chamber and a pair of oppositely disposed slots opening into said chamber, an inner connector assembly positioned within said housing, said assembly having a first plurality of individual spring elements, a ground plane spring, said ground plane spring having a central portion and a plurality of second spring elements integral with said central portion and projecting transversely thereof, a dielectric member disposed between said first plurality of individual spring elements and said ground plane spring and providing a predetermined spacing therebetween, a first insulating member having a plurality of slots, said member disposed on one side of said assembly and adapted to receive within said slots said first spring elements, and a second insulating member disposed on the other side of ,said assembly, said first and said second members sandwiching said assembly therebetween.

2. The electrical connector of claim 1 wherein said first spring elements and said second spring elements of said ground plane spring are staggered with respect to each other and have inwardly curved spring portions overlying said slots in said housing.

3. The electrical connector of claim 1 wherein said housing comprises a pair of shells, and complementary means are provided on said shells and said inner connector assembly to lock said assembly within said shells.

4. The electrical connector of claim 3 wherein said shells are provided with fastener means to secure said shells together.

5. An electrical connector comprising a housing, said housing having a first elongated shell and a second elongated shell, each of said shells being provided respectively with an axially running slot on the outer face thereof and an inner chamber opening onto said slot, said chambers being disposed opposite each other and forming a single chamber when said shells are mated to form said housing, and an inner connector assembly comprising a ground plane spring, said ground plane spring having a central portion and a plurality of spring elements projecting transversely of said central portion on either side thereof, a plurality of individual spring elements spaced from said ground plane spring and extending longitudinally in generally the same direction as said ground plane spring elements, a dielectric spacer bar maintaining said individual spring elements and said ground plane spring spaced from each other a predetermined distance, a first insulating member having a plurality of slots, said member disposed on one side of said assembly and adapted to receive within said slots said first spring elements, and a second insulating member disposed on the other side of said assembly, said first and said second members sandwiching said assembly therebetween.

5 6 6. The electrical connector of claim 5 wherein said References Cited shells and said inner connector assembly are provided UNITED STATES PATENTS with complementary locking means to lock said assem- 3,093,805 6/1963 o if hi et aL bly within said shells. 3,149,893 9/1964 Dupre 33914 7. The electrical connector of claim 5 wherein said 5 1( fi f rlmmlns iiig W1 th fastening means to secure 3,179,904 4/1965 Paulsen 174-36 X 3,356,983 12/1967 Johnson 33914 8. The electrical connector of claim 5 wherein the inner surfaces of said shells are provided wtih a plurality RICHARD MOORE, Primary Examiner of notches to receive said ground plane spring elements s 1 and said individual spring elements. 339-176, 206 

